The league is asking a court to force researchers at the CTE Center at Boston University to release confidential information players, concussion studies, and significantly, on findings that relate to the neurodegenerative disease known as "Chronic Traumatic Encephalopathy" or CTE.

Charles Zimmerman is co-lead counsel for the former players. He says the NHL is taking a page from "big tobacco's" playbook and joins Bob McDonald to explain.

Bob McDonald also speaks with Dr. Carmela Tartaglia about what the science shows about concussions and their relationship to CTE. She's a clinician and scientist at the Tanz Centre for Research in Neurodegenerative Diseases at the University of Toronto.

The NHL did not respond to requests for comment on this story.

The photo on the left shows abundant tau tangles (dark brown dots) in the cerebral cortex in a pattern unique to chronic traumatic encephalopathy (CTE). A higher magnification image on right shows a closer view of the tangles in nerve cells. The NHL is questioning the link between concussions and CTE. ((Center for the Study of Traumatic Encephalopathy) )